- Topic in Gardening courses
Soil pH is a measure for how many H+ ions a soil contains. pH is a measure of how acidic or basic things are.
pH is defined as the negative logarithm (base 10) of the activity of hydrogen ions (H+) in solution. It ranges from 0 to 14, with 7 being neutral. A pH below 7 is acidic and above 7 is basic.[1] A pH of 6 means that there are 10 times more H+ ions in the soil compared to pH 7, while a pH of 3 means, for example, that there are 10,000(104) times more H+ ions in solution compared to pH 7.
Substances such as lemon juice and battery acid are acidic and fall in the 0-7 range, whereas seawater and bleach are basic (also called "alkaline") and fall in the 7-14 pH range. Pure water is neutral, or 7 on the pH scale.
Soil pH controls many chemical processes that take place in the soil. It specifically affects plant nutrient availability by changing the chemical form in which these nutrients are available. The optimum pH range for most plants is between 6 and 7.5, but many plants have adapted to pH values outside this range.
Classification of soil pH ranges
Denomination | pH range |
---|---|
Ultra acid | <3.5 |
Extreme acid | 3.5 - 4.4 |
Very strong acid | 4.5 - 5.0 |
Strong acid | 5.1 - 5.5 |
Moderate acid | 5.6 -6.0 |
Slight acid | 6.1 -6.5 |
Neutral | 6.6 - 7.3 |
Slightly alkaline | 7.4 - 7.8 |
Moderately alkaline | 7.9 - 8.4 |
Strongly alkaline | 8.5 -9.0 |
Very strongly alkaline | >9.0 |
Source: The United States Department of Agriculture Natural Resources Conservation Service
Plant pH preferences
- This list is still under construction and needs to be checked with various sources
- pH 4.5-5.0 Blueberry, Bilberry, Heather, Cranberry, Orchid, Azalea
- pH 5.0 - 5.5 Parsley, Potato, Heather, Pine, Maize, Radish, Ferns, Iris, Rhododendron
See also
References
External links
- Soil pH Wikipedia